A solid battery using a high-molecular solid electrolyte has recently come into the limelight because the solid battery has the merits that the possibility of the occurrences of a liquid leakage, igniting, gas spouting, etc., is generally low as compared with a battery using a conventional electrolytic solution and can ensure a higher reliability about safety. However, because the electric conductivity of the solid electrolyte is relatively low as compared with that of a conventional electrolytic solution, the internal resistance of the solid electrolyte becomes high, when the solid electrolyte is used for a solid battery, only the battery having a very small capacity is obtained, which closes the application of a solid electrolyte for a thin and light solid battery having a high capacity.
To develop a high-capacity battery using a solid electrolyte, a solid electrolyte obtained by mixing an acryloyl-modified high-molecular compound having an alkylene oxide polymer chain, an electrolyte salt, and further a solvent optionally, and crosslinking the mixture by the action of heat, light, electron beams, etc., is proposed. As conventional techniques, there are, for example, a high-molecular solid electrolyte by a combination of a trifunctional polymer having a terminal acryloyl-modified alkylene oxide polymer chain, a low-molecular alkylene oxide copolymer, polyvinyl chloride, an electrolyte salt, etc., as described in Japanese Patent Laid Open No. 3-177409; a solid electrolyte by a combination of a terminal acryloyl-modified alkylene oxide copolymer, an inorganic ion salt, and an organic solvent such as propylene carbonate, etc., as described in Japanese Patent Laid Open No. 63-94501; and a solid electrolyte by a combination of a difunctional and/or monofunctional high-molecular compound having terminal acryloyl-modified alkylene oxide polymer chain and an electrolyte salt as described in Japanese Patent Laid Open No. 5-178948. However, these solid electrolytes are not always satisfactory ones from the view points of a high capacity and a high mechanical strength.